U.S. Pat. No. 7,912,236, discloses a sound transducer structure having a perforated backplate with multiple circular through holes extending through the backplate. However, if the diameters of the circular through holes formed in the backplate are overlarge, alien particles would easily pass through those large circular holes and drop into the sound cavity of the sound transducer structure, which may form a leakage path, resulting in the microphone being disabled.